Auto transformer silver boat

ABSTRACT

This is a silver boat apparatus wherein one end of the induction coil is connected to the header of the crucible which is adapted for pouring. This results in the pouring end of the crucible being directly heated for greater efficiency while the remaining portion of the crucible is still heated by eddy currents which is sufficient for melting the metal being treated.

United States Patent [72] Inventors Henley Frank Sterling [56] References Cited was; Md G H I be h f UNITED STATES PATENTS En 3.l08,l69 10 1963 Keller 219 1049 A I No 8615 3,377,565 4/1968 Denner 219/1079 X 3,441,706 4/1969 Van Steyn. 219/1079 x PM 3461215 8/1969 R b 13/27 145 Patented June 22, 1971 1 e aux (731 Assignee International Standard Electric Primary Examiner-J. V. Truhe Corporation Assistant ExaminerL. H. Bender New York, NY. Attorneys-C. Cornell Remsen, .lr., Walter J. Baum, Paul W. [32] Priority Oct. 17, 1968 Hemminger, Percy P. Lantzy, Philip M. Bolton, Isidore [33] Great Britain Togut and Charles L. Johnson, .lr. l 1 49.296/68 [54] AUTO TRANSFORMER SILVER BOAT 3 Claims 3 Drawing 7 ABSTRACT: This is a silver boat apparatus wherein one end [52] US. Cl 13/27, of the induction coil is connected to the header of the crucible 1 2 l9/ 10.49, 2 19/1 0.79 which is adapted for pouring. This results in the pouring end of I [51 1 Int. Cl H05b 5/00, the crucible being directly heated for greater efficiency while H05b 9/02 the remaining portion of the crucible is still heated by eddy [50] Field of Search 219/ 10.49, currents which is sufi'icient for melting the metal being treated.

AUTO TRANSFORMER SILVER BOAT BACKGROUND OF THE l.\'\ ENTlON This invention relates to apparatus for the heat treatment of electrically conductive materials. having particular application to the melting or other heat treatment of materials that are highly reactive when hot and hence are particularly liable to contamination during treatment by the material of which a containing crucible is made.

Various forms of noncontaminating crucible and/or heat treatment apparatus are described in British Pat. specifications No. 827,676 (R. W. Warren-l) and N0. 44,728/68 (W. R. George-6); and U.S. applications No. 795,718 filed Feb. 26, 1959 H. F. Sterling, F. J. Raymond, R. W. Warren 17-9-3 now abandoned and No. 734,614 filed June 5. 1968 (H. F. Sterling, F. H. Edwards 46-] now U.S. Pat. No. 3,531,574.

In each of these forms, the crucible is hollow walled and constructed of a metal of high electrical and thermal conductivity. For the purposes of this specification, a metal of high electrical and thermal conductivity is defined as a metal having a thermal conductivity of not less than 0.49 gram calories per sec. per cm. per C. per cm., and a specific electrical resistance of not more than 2.66Sxl ohms per cm. at 0 C. Silver, gold and copper are suitable metals, silver being preferred since it can be highly polished to reduce the loss of heat from the charge by radiation. Alloys of these metals may be employed or a surface coating of one metal such as silver on a member made of another metal such as copper.

For each of the crucibles described in the above mentioned patent specifications and applications, heating of the charge contained by the crucible is by inducing circulating currents in the crucible wall, and hence raising the temperature of the charge by eddy current heating, by a separate primary induction coil surrounding the crucible, and normally separated therefrom by an intervening quartz enclosure to contain a reducing or inert gaseous atmosphere around the charge.

While such an arrangement of a separate primary induction coil is perfectly satisfactory for heat treatment processes of the charge such as solid purification or zone refining when the charge remains. in the crucible, in other heat treatment processes where it is desired to pour the molten charge from the crucible, the configuration of the crucible at the pouring point may be such that the current induced therein by the primary induction coil is insufficient to obtain adequate powerto be coupled in to melt the charge sufficiently for satisfactory pouring.

SUMMARY OF THE INVENTION BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a side elevation of apparatus for the heat treatment of electrically conductive materials;

FIG. 2 is a plan view of the apparatus; and

FIG. 3 is an end elevation of the apparatus sectioned along the line A-A of FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENT The apparatus, shown in its horizontal operating position, comprises a crucible of a semiannular cluster of tubes I of metal of high electrical and thermal conductivity, such as silver plated copper, spaced sufficiently closely side by side to prevent molten charge material from escaping, the tubes I defining at their inner longitudinal surfaces a charge-containing volume of semicircular cross section.

At one end of the crucible the tubes 1 terminate in a silverplated copper header tube 2 serving as a cooling fluid outlet manifold. The other ends of the tubes terminate in a semiannular end wall 3 ofa hollow member 4 of metal of high electrical and thermal conductivity, such as silver-plated copper, the tubes 1 communicating internally with the interior of the hollow member 4. i

The inner surface 5 of the member 4 extending away from the end wall 3 is initially shaped to conform with the semicircular outline of the tube-defined charge-containing volume, and then rises with an inward taper to the upper surface level of the crucible to provide a pouring lip 6 for the crucible.

'In addition to functioning as a pourer, the member 4 also serves as a cooling fluid inlet manifold for the tubes 1, and is provided with a cooling fluid inlet pipe 7.

Rigidly connected to the upper surface of the member 4 diametrically opposite to the point of entry of the inlet pipe 7 and internally communicating with the hollow interior of the member 4 is one end of primary induction coil 8 of a metal tube of high electrical and thermal conductivity, such as copper. The induction coil 8 surrounds the tube cluster length of the crucible.

In operation, with the crucible loaded with a charge of material for processing, the inlet pipe 7 is connected to a source of cooling fluid, the cooling fluid circulating both to the crucible components of hollow member of tubes 1 and outlet manifold 2, and also through the induction coil 8.

Electrical connection is made to a suitable source of high frequency current, one connection from the inlet pipe '7 and the other connection from the free end 8A of the induction coil. The inlet pipe 7 is earthed, or connected to the earthy end of the oscillatory circuit.

The primary current path is therefore via the inlet pipe 7, the inner surface 5 of the pourer 4 and the induction coil 8.

Over the tube cluster length of the crucible, secondary circulating currents in the tubes cause eddy current heating of the charge, while at the pouring end of the crucible, the charge is heated by the primary current.

This ensures adequate heating of the charge at the pouring end of the crucible for pouring the charge by rotating the crucible sufficiently to allow the charge to pour over the pouring lip 6.

Due to the integral construction of the primary induction coil with the crucible, with the earthy end of the coil common with the crucible, there is reduced any tendency to form a glow discharge or arcing effect.

The apparatus may be used for material processing requiring a controlled atmosphere, when the apparatus is surrounded by a suitable enclosure for maintaining the desired atmosphere such as a reducing or inert atmosphere at the required pressure.

The described autotransformer arrangement of integral primary induction coil may be utilized with other forms of noncontaminating hollow-walled crucibles of metal of high electrical and thermal conductivity, described in the previously mentioned patent specifications and applications.

We claim:

I. Apparatus for the heat treatment of electrically conductive materials, comprising:

, a hollow-walled crucible of a metal of high electrical and thermal conductivity, as hereinbefore defined, said crucible having a pouring lip at one end thereof; and

a primary induction coil surrounding said crucible and connected to the inner surface of said pouring lip.

2. Apparatus as claimed in claim 1 wherein said induction 

2. Apparatus as claimed in claim 1 wherein said induction coil comprises a tube of a metal of high electrical and thermal conductivity, and there being a common cooling fluid connection for both the crucible walls and said induction coil.
 3. Apparatus as claimed in claim 1 wherein that portion of said crucible other than at said pouring lip comprises a number of tubes of metal of high electrical and thermal conductivity arranged sufficiently close together for molten material to be prevented from escaping therefrom. 